1. Field of the Invention
The present invention relates to a resin-molded product which is inhibited from yellowing. The yellowing results from a phenol-based oxidation inhibitor. Moreover, the present invention also relates to a yellowing inhibitor agent which can appropriately inhibit the yellowing.
2. Description of the Related Art
Oxidation inhibitors are added to many resin-molded products, for instance, polyolefin-based resin-molded products such as automobile resin-molded bumpers to inhibit resin-molded products from thermally deteriorating during molding operations, or during services.
As for the oxidation inhibitors, it is possible to exemplify phenol-based oxidation inhibitors, phosphorus-based oxidation inhibitors, and sulfur-based oxidation inhibitors. Among the oxidation inhibitors, the phosphorus-based oxidation inhibitors are used for resin-molded products to which an elevated temperature of 200.degree. C. or more is applied. The phenol-based oxidation inhibitors and sulfur-based oxidation inhibitors are used for resin-molded products to which a relatively low temperature of from 80 to 100.degree. C. is applied. In particular, the phenol-based oxidation inhibitors are usually used for resin-molded products such as automobile resin-molded bumpers, because the sulfur-based oxidation inhibitors were found to induce coloring when they are used together with light-slabilizing agents, such as HALS (Hindered Amine Light Stabilizer).
Resin-molded products such as automobile resin-molded bumpers are usually painted with acrylic-melamine-based paints, or the like, in order to make final products. However, the phenol-based oxidation inhibitors have been known to cause yellowing in the acrylic-melamine-based paint films. Accordingly, instead of the phenol-based oxidation inhibitors, it is necessary to select an oxidation inhibitor, which is less likely to cause yellowing in the acrylic-melamine-based paint films, for automobile bumpers.
The phenol-based oxidation inhibitors are believed to cause yellowing in the acrylic-melamine-based paint films in the following manner: coloring substances (i.e., reactants resulting from the phenol-based oxidation inhibitors), or the phenol-based oxidation inhibitors themselves migrate from resin-molded products into the paint films, and eventually they are visible from the outside.